Computers generally require a media in which digital data can be stored and retrieved. Magnetizable (hard) layers on discs have proven to be a reliable media for data storage and retrieval. However, other types of disc drives, such as optical disc drives, are also frequently used. Disc drives that read data from and write data to hard discs have become popular components of computer systems.
To access a memory location or data block on a hard disc a read/write head is positioned above the surface of the disc while the disc rotates at an essentially constant velocity. By moving the read/write head radially over the rotating disc, all memory location on the disc can be accessed. This is typically referred to as “flying” because the head is coupled to a slider that is hydrodynamically configured to hover over the surface of the disc on a cushion of air.
In a conventional disc drive, multiple discs are coupled to and rotate about a spindle. Each of the discs has two substantially flat surfaces that are capable of storing data. Typically these discs are stacked in a parallel relationship with each other. The heads are designed to move within the space between adjacent discs while flying close to the disc surface. The head is coupled to the distal end of a thin, arm-like structure called a head suspension assembly (HSA), which is inserted within the space between two adjacent discs. This HSA is made of materials and thickness so as to be somewhat flexible and to allow a measure of vertical positioning as the head hovers over the surface of the rotating disc.
Typically, HSAs are mounted and supported by an actuator arm. An actuator arm is selectively positionable by a rotary actuator assembly over a selected data track or data block of the disc to either read data from or write data to a selected data block. Historically, this actuator assembly has assumed many forms, with most disc drives of the current generation incorporating an actuator of a type referred to as a rotary voice coil actuator. Typically the rotary voice coil actuator consists of a pivot attached to a drive housing of the disc drive. A shaft is mounted and set such that its central axis is normal to the plane of rotation of the disc. An actuator housing is pivotally mounted to the pivot shaft and supports a coil which is supported in a magnetic field generated by an array of permanent magnets. When controlled direct current is applied to the coil, an electromagnetic field is formed which interacts with the magnetic field of the permanent magnet that is in proximity to the coil. This causes rotation of the actuator housing in accordance with the well-known Lorentz relationship. As the actuator housing rotates, the read/write head is moved radially across the data tracks on the disc. Control of the movement of the head from track to track on the disc surface is commonly accomplished through the use of the closed loop servo system. When an access command is sent to the disc drive, a comparison is made between the current position of the head relative to the disc and the location of the desired data transfer on the disc. If the head is currently positioned over the desired track, the disc drive simply waits for the correct circumferential location to rotate under head, and then begins the requested data transfer. If however this transfer is to take place at a location other than the present position of the actuator, servo logic determines both the distance and direction that the actuator must move in order to bring the head over the target track. Based on this determination, servo logic applies controlled direct current to the coil of the actuator voice coil motor, which causes the actuator to move from the current track location to the desired target track.
A conventional prior art actuator requires a large number of components from a mechanical and electrical viewpoint. As there are a number of components in the actuator the time and effort required to assemble the actuator is very high. Further, each actuator needs to be tested to ensure that it will properly operate and in order to determine a relatively acceptable yield of the group of actuators thus adding to the time required to manufacture the drive. This testing and assembly results in a relatively high cost for assembling the actuator for use in a disc drive. Therefore, there is a desire for a low cost system that can be achieved by optimizing the supply chain process or targeting a design point to achieve a 100% yield across all of the components without a test.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.